export function isValidMenuItems(menu: IUserFriendlyMenuItem[], collector: ExtensionMessageCollector): boolean {
		if (!Array.isArray(menu)) {
			collector.error(localize('requirearray', "menu items must be an array"));
			return false;
		}

		for (let item of menu) {
			if (typeof item.command !== 'string') {
				collector.error(localize('requirestring', "property `{0}` is mandatory and must be of type `string`", 'command'));
				return false;
			}
			if (item.alt && typeof item.alt !== 'string') {
				collector.error(localize('optstring', "property `{0}` can be omitted or must be of type `string`", 'alt'));
				return false;
			}
			if (item.when && typeof item.when !== 'string') {
				collector.error(localize('optstring', "property `{0}` can be omitted or must be of type `string`", 'when'));
				return false;
			}
			if (item.group && typeof item.group !== 'string') {
				collector.error(localize('optstring', "property `{0}` can be omitted or must be of type `string`", 'group'));
				return false;
			}
		}

		return true;
	}

	function isValidLocalizedString(localized: string | ILocalizedString, collector: ExtensionMessageCollector, propertyName: string): boolean {
		if (typeof localized === 'undefined') {
			collector.error(localize('requireStringOrObject', "property `{0}` is mandatory and must be of type `string` or `object`", propertyName));
			return false;
		} else if (typeof localized === 'string' && isFalsyOrWhitespace(localized)) {
			collector.error(localize('requirestring', "property `{0}` is mandatory and must be of type `string`", propertyName));
			return false;
		} else if (typeof localized !== 'string' && (isFalsyOrWhitespace(localized.original) || isFalsyOrWhitespace(localized.value))) {
			collector.error(localize('requirestrings', "properties `{0}` and `{1}` are mandatory and must be of type `string`", `${propertyName}.value`, `${propertyName}.original`));
			return false;
		}

		return true;
	}

	export function isValidCommand(command: IUserFriendlyCommand, collector: ExtensionMessageCollector): boolean {
		if (!command) {
			collector.error(localize('nonempty', "expected non-empty value."));
			return false;
		}
		if (isFalsyOrWhitespace(command.command)) {
			collector.error(localize('requirestring', "property `{0}` is mandatory and must be of type `string`", 'command'));
			return false;
		}
		if (!isValidLocalizedString(command.title, collector, 'title')) {
			return false;
		}
		if (command.category && !isValidLocalizedString(command.category, collector, 'category')) {
			return false;
		}
		if (!isValidIcon(command.icon, collector)) {
			return false;
		}
		return true;
	}

	function isValidIcon(icon: IUserFriendlyIcon | undefined, collector: ExtensionMessageCollector): boolean {
		if (typeof icon === 'undefined') {
			return true;
		}
		if (typeof icon === 'string') {
			return true;
		} else if (typeof icon.dark === 'string' && typeof icon.light === 'string') {
			return true;
		}
		collector.error(localize('opticon', "property `icon` can be omitted or must be either a string or a literal like `{dark, light}`"));
		return false;
	}

	export function from(value: TaskDefinition, extensionId: string, messageCollector: ExtensionMessageCollector): Tasks.TaskDefinition | undefined {
		if (!value) {
			return undefined;
		}
		let taskType = Types.isString(value.type) ? value.type : undefined;
		if (!taskType || taskType.length === 0) {
			messageCollector.error(nls.localize('TaskTypeConfiguration.noType', 'The task type configuration is missing the required \'taskType\' property'));
			return undefined;
		}
		let required: string[] = [];
		if (Array.isArray(value.required)) {
			for (let element of value.required) {
				if (Types.isString(element)) {
					required.push(element);
				}
			}
		}
		return { extensionId, taskType, required: required, properties: value.properties ? Objects.deepClone(value.properties) : {} };
	}